Cards, such as identification cards, transponder cards, and transaction cards, such as credit cards, debit cards, sometimes referred to as smart cards, are well known in the art, some embodiments of which may comprise one or more metal layers. An exemplary such card is shown in U.S. Pat. No. 8,725,589, incorporated herein by reference. It is also well known to embed a microchip or payment module in transaction cards, including in metal cards. Some embedded payment modules, referred to as “dual interface” modules, have contacts disposed on one side of the card and configured to interface with a card reader, and a radio frequency identification (RFID) antenna for communicating inductively with a card reader. In a metal environment, such as a metal card, it may be necessary to provide a booster antenna or amplifier to improve performance of the communication interface with the card reader.
In particular, it is known to use the metal frame of the card itself as such an antenna or amplifier, with the metal enclosure that surrounds the payment module chip having a discontinuity or “slit” in the metal. U.S. Pat. No. 8,608,082 ('082 Patent) to Le Garrec et al. and U.S. Pat. No. 9,812,782 (and others), to Finn et al., incorporated herein by reference, disclose metal cards with such a discontinuity in the form of a slit emanating from a mounting location of the RFID chip in the card to a peripheral edge of the card. The concept of a metal, card-shaped, non-contact antenna having a slit, for RFID signal amplification in a metal environment, is also described generally in the literature, such as at “A Metallic RFID Tag Design for Steel-Bar and Wire-Rod Management Application in the Steel Industry,” Progress In Electromagnetics Research (PIER) Vol. 91 (2009).
The '082 Patent characterizes the metal frame of the card as an amplifier for amplifying the gain of the near-field communication antenna electrically connected to the microcircuit associated with the payment module, the amplifier comprising “an electrically conductive element electrically insulated from the microcircuit and from the antenna, of generally annular shape,” which in some embodiments forms a ring that is broken at least once.
The Finn patents refer to the payment module as a “transponder chip module (TCM) comprising an RFID chip (IC) and a module antenna” and describes the amplifier formed by the card body as a “coupling frame” having “an electrical discontinuity comprising a slit or non-conductive stripe.”
Regardless of the nomenclature used, metal “slit” cards may have some disadvantages. In particular, embodiments in which a single slit extends from a midpoint of one edge of the module pocket to the periphery of the card in a straight horizontal line that is the shortest path from the pocket to the periphery provides little resistance to flexure of the card at the discontinuity. Metal cards may still have one or more layers over the metal layer. For a card in which the one or more layers is plastic, the plastic may start to wear or whiten because of such flexure. Thus, there is a need in the art for designs that provide better resistance to card flexure and the potential wear induced thereby. Although Finn proposes some alternative constructions, there is still a need in the art for constructions that provide improved functionality and aesthetics.